With "Hot Rod," comedian Andy Samberg tries to make the massive jump from "Saturday Night Live" to the big screen. And, like the amateur stuntman he plays in the film, he often looks as though he's going to make it "» before crashing brutally to the ground.

The reason for the failure is simple, and screenwriter Pam Brady owns a big share of the blame: There just isn't enough to "Hot Rod" for an 88-minute feature.

The plot revolves around man child Rod Kimble's (Samberg) unfulfilled dream of becoming a professional stuntman. Because he's not good enough to get any real work -- and because he attempts all his jumps using a moped -- he has to self-produce his tricks with a team made up of his half-brother, Kevin (Taccone), his buddies Dave (Bill Hader) and Rico (Danny R. McBride) and the girl of his dreams, Denise (Isla Fisher).

None of them know what they're doing, and the pay off is a series of colossal crashes that are among the best physical comedy bits I've seen in years. Alas, a funny movie requires more than men setting themselves on fire and crashing into milk trucks, pools, vans, "». Actually, any movie that isn't branded "Jackass" requires more than men setting themselves on fire and crashing into milk trucks, pools, vans. etc.

As funny as the failed stunts are, "Hot Rod" desperately needs some mortar to fill the gaps between action sequences.

Brady tried to create that with Rod's love-hate relationship with his stepfather, Frank (Ian McShane), the type of guy who shows his love by making his kids tougher. For Rod, that means weekly, no-holds barred fights in the family basement. Rod's main goal in life is to kick Frank's ass so that he can gain his respect.

It's devastating, then, when Rod learns that Frank is dying of a heart ailment and will never be well enough to fight again. Without wasting a second, Rod pledges to stage the biggest stunt of his life, raise enough money to get Frank a new heart, then beat the tar out of him.

As silly as it sounds, this aspect of the story works remarkably well and Samberg's battles with McShane are littered with more great physical comedy. Sadly, for every gag that works there's at least one that falls dead.

The good news here is that Andy Samberg and company infused "Hot Rod" with enough talent and funny moments to prove that they probably have what it takes to make a great comedy. The bad news is this isn't it.